The synthesis and characterization of Co(II) and Co(III) 2,6-
pyridinedicarboxylate (di
pic
2-) com
plexes are re
ported.Solid-state X-ray characterizations were
performed on [Co(H
2di
pic)(di
pic)]·3H
2O and [Co(di
pic)(
-di
pic)Co(H
2O)
5]·2H
2O. Two coordination modes not
previously observed in di
picolinate transition metal com
plexes were observedin these com
plexes; one involves metal coordination to the short C-O (C=O) bond, and the other involves metalcoordination to a
protonated oxygen atom. Solution studies, including
paramagnetic NMR and UV-vis s
pectrosco
py,were done showing the high stability and low lability of the Co(III) com
plex, whereas the Co(II) com
plexes exhibitedligand exchange in the
presence of excess ligand. The [Co(di
pic)
2]
2- com
plex has
pH de
pendent lability and in thisregard is most similar to the [VO
2di
pic]
- com
plex. The [Co(di
pic)
2]
2- was found to be effective in reducing thehy
perli
pidemia of diabetes using oral administration in drinking water in rats with STZ-induced diabetes. Oraladministration of VOSO
4 was used as a
positive control for metal efficacy against diabetes. In addition to
providinga framework to evaluate structure-function relationshi
ps of various transition metal com
plexes in alleviating thesym
ptoms of diabetes, this work describes novel as
pects of structural and solution cobalt chemistry.